De Kock combined well with Temba Bavuma to stitch a 173-run partnership with de Kock scoring a ton and Bavuma just missing out on the triple figure mark after he was contentiously dropped from South Africa's test team in the recent series against England.
South Africa put England in to bat at Newlands in Cape Town and had the visitors reeling at 131-6. England eventually posted 258-8 in its 50 overs. South Africa chased down the target with relative ease with two overs and two balls to spare.
England won that Test series 3-1 but didn't have the same success in its first ODI since the dramatic win over New Zealand in a Super Over in the Cricket World Cup final last July.
Joe Denly, one of just four players remaining from last month's test series triumph, made 87 to lift England out of trouble. He was helped by Chris Woakes, another man who played that test series, who made 40 off 42 balls. The pair shared a 92-run stand for the seventh wicket.
South Africa's chase was comfortable, though, after de Kock and Bavuma combined to take the Proteas from 25-1 to 198-2 when de Kock was out bowled by Joe Root for 107. De Kock hit 11 fours and a six, and opened the batting and kept wicket as well as leading the team for the first time after his appointment to succeed Faf du Plessis.